When it comes to eating, there are few rules we all tend to agree with. 'Don't chew with your mouth open' and 'don't talk with your mouth full' are among the most obvious yet most frequently broken.
But according to scientists in Australia, there is one that could pose a threat to your health. I am of course talking about the double dip.
Food expert Paul Dawson, the author of Did You Just Eat That?, has carried out multiple studies on the disgusting eating habit and found it was more dangerous than abiding by the 'five-second rule'.
Speaking to ABC Radio Perth, he said he was shocked after testing his theory by taking a second swipe of food into communal bowls of chocolate dip and salsa.
He said: "I expected there to be not really much bacteria transfer because of the small surface area on a cracker or chip when you bite it.
"But we actually found there was 1,000 more bacteria per millilitre in the dip from when you bit the chip than when you didn't.
Double dipping has '1,000 more bacteria per millilitre in the dip from when you bit the chip than when you didn't'. Credit: PA
"That's a significant amount ... that's more like a person-to-person transfer like the common cold and other contagious diseases rather than the typical food-borne illness like E.coli and salmonella."
The professor then looked at the well-known and much-loved 'five-second rule' - the excuse used largely by teenage boys to continue eating food after it's fallen on the floor. Quick recap if you've forgotten: it was picked up within five seconds then it was ok to eat.
Putting this theory to the test, Prof Dawson said: "It's kind of like you're playing Russian roulette.
"It depends on the surface - if there is pathogenic bacteria on that surface, then no, it is not safe to eat.
"But honestly, most surfaces are not going to have any kind of dangerous bacteria there."
Prof Dawson said its best to avoid double dipping and eating from the floor. Credit: PA
He added: "Most of us have probably used the five-second rule and not gotten sick, but again it depends on the surface."
If you are going to continue to live by the 'five second rule' however, Prof Dawson said it's worth bearing in mind that carpets actually soak up some of the bacteria they tested, such as salmonella.
He said: "The carpet actually soaked up the salmonella we placed on it.
"The carpet fibres stick up and so there wasn't much salmonella to be in contact with the bread and baloney we dropped."
But even with this information to hand, it's still best to play it safe in certain situations.
"If you're in a place where people are preparing raw food, it may not be a good idea," he added.
And if Donald Trump says don't do it, you probably shouldn't.
Featured Image Credit: PA